If you solve a system and end up with the equations $\displaystyle{x}={0}\usepackage{cmbright}\Huge\$ and $\displaystyle{y}={1}\usepackage{cmbright}\Huge\$ , then that would mean the solution is (0, 1). For this system, both equations being true would imply that $\displaystyle{0}={1}\usepackage{cmbright}\Huge\$ . But this is false, which means that you cannot find numbers that make both equations true.